- Test Setup
- The 1st Series of Tests
- The 2nd Series of Tests
- Analysis of Results

Prior to these tests I had ordered a 363mm Tania Koba twist barrel and a 363mm KM Teflon 6.04mm tightbore barrel from WGCShop. I was hoping to see what accuracy difference there might be between the two. Half way through the tests I realized that the KM barrel was actually 407mm. WGC sent me the wrong barrel. Since I still wanted a 363mm tightbore I decided to order a Promethius, 363mm x 6.03mm tightbore to add another dimension (bore diameter) to the tests. The following barrels were tested using the procedures set forth in the test:

1. 247mm x 6.08mm CA stock inner barrel
2. 300mm x 6.04mm KM Teflon inner barrel
3. 363mm Tania Koba Twist inner barrel
4. 363mm x 6.03mm Promethius inner barrel
5. 407mm x 6.04mm KM Teflon inner barrel

As you can see in the photo I placed my CA G36c into a rifle stand, on a folding table pointing down range to carefully measured distances. Granted, my rifle stand is not a very expensive, elaborate one but it did serve adequately in these tests. My target was the standard 25-yard pistol slowfire target found at Walmart. The target was 11” x 16”, taped to a corrugated box with a brick in the box for stability against wind and shot vibration. The box helped by allowing me to hear the shots striking the target.

The CA G36c was newly upgraded and consisted of the following gearbox internals:
1. PDI 140 spring,
2. Systema Silent Head set,
3. Promethius bearing spring guide,
4. Guarder steel gear set,
5. Guarder enhanced tappet plate,
6. Guarder air seal nozzle, and
7. Guarder cylinder for 363mm inner barrel.

At the time of the first test the upgrades had less than 200 shots through the gun.

The test procedure was worked out by sighting the G36c to the center of the target using a laser bore sight. Then I would adjust the hop-up until my shots were level with the center of the target for the given distance and given bb weight. At each distance I would shoot 10 shots with each bb weight, changing to a fresh target for each group of 10 shots. Between each shot a three-count pause allowed any vibration from the shot to dissipate.

1st Series
of Tests

Dec 9 & 15, 2006

KM Teflon 407mm x 6.04mm barrel test - December 9, 2006 – starting 2:00pm, 42 degF, no wind.

0.20 Perfect bbs: Average fps = 369.77
Chrono’ed 10 shots: 371.7, 368.9, 369.5, 371.7, 368.8, 365.7, 372.5, 371.1, 367.2, 370.6

0.25 Elite bbs: Average fps = 335.11
Chrono’ed 10 shots: 336.2, 336.3, 335.0, 336.5, 334.9, 333.6, 334.5, 334.3, 335.3, 334.5

These first three tests became the benchmark for the rest of the tests to come. The results were pretty much what I expected and I was happy to see a definite improvement in accuracy when using the heavier 0.25 bbs. I ran out of sunlight before I could test 0.20 bbs at 100’. However, I suspect the shot group might extend beyond the width of my target.

Tania Koba 363mm Twist barrel test – December 15, 2006 – starting 3:30pm, 64 degF, no wind. (note: The AEG had approx. 1500 bbs shot through it between the KM barrel test and this barrel test. This, I believe explains the significant drop in fps from the KM barrel and the TK barrel. According to the experience of others, the Twist barrel also lowers fps as a result of having a larger bore diameter.)

0.20 Perfect bbs: average fps = 346.1
Chrono’ed 10 shots: 348.2, 348.5, 344.9, 345.4, 347.8, 344.2, 344.5, 348.0, 346.1, 343.5

0.25 Elite bbs: Average fps = 311.3
Chrono’ed 10 shots: 309.1, 310.1, 312.8, 310.5, 315.1, 311.8, 312.4, 309.4, 312.0, 309.5




Results show a significant improvement in accuracy over the KM Teflon, 407mm barrel, especially when using 0.25 bbs. The fact that the fps of the G36c was closer to the Twist barrel’s maximum effective fps probably had some affect on the comparative results. Regardless, the TK barrel appears to be a good choice of barrels for lower powered AEGs.

2nd Series
of Tests

Jan 20, 2006

Starting 10:00am, 45 degF, 5-10 mph right to left cross wind

(note: Added 0.28 bbs to the tests).

Even though my original intent was to only compare the KM Teflon barrel against the TK Twist barrel it became apparent that I could get a more definitive test if I added the stock CA, 247mm barrel and a 300mm KM Teflon barrel to the mix. No bbs were fired through the G36c between the Dec. 15th tests and this series of tests.)

CA stock 247mm x 6.08mm barrel test

0.20 Elite bbs: Average fps = 329.3
Chrono’ed 10 shots: 328.0, 330.0, 329.9, 331.9, 328.6, 327.8, 327.7, 329.1, 329.0, 330.5

0.25 TSD bbs: Average fps = 303.5
Chrono’ed 10 shots: 300.5, 304.8, 302.1, 305.3, 304.8, 305.1, 303.0, 304.1, 302.3, 303.4

0.28 TSD bbs: Average fps = 279.2
Chrono’ed 10 shots: 278.5, 281.6, 277.5, 279.1, 280.0, 279.3, 276.6, 281.3, 275.5, 282.3

The results with the stock inner barrel were a bit confusing. The accuracy was decent by test standards but as expected it was less accurate than some of the other inner barrels. As for the narrowness of the 0.28 bb group I can only guess that there was a short time when no wind was affecting the shots.

KM Teflon 300mm x 6.04mm barrel test

0.20 Elite bbs: Average fps = 347.6
Chrono’ed 10 shots: 346.4, 346.4, 347.6, 348.0, 349.3, 348.5, 348.1, 346.0, 347.4, 347.8

0.25 TSD bbs: Average fps = 317.0
Chrono’ed 10 shots: 318.5, 314.2, 318.3, 317.2, 316.7, 315.6, 320.3, 316.5, 316.7, 316.3

0.28 TSD bbs: Average fps = 290.5
Chrono’ed 10 shots: 292.8, 292.4, 287.8, 294.1, 288.3, 290.9, 291.9, 288.2, 289.8, 288.4

The results for the 300mm KM inner barrel were pretty much as expected. There is a definite improvement over the stock barrel. It is interesting to note how much more accurate a heavier bb is than the 0.20 bb. The breeze during the tests was causing the shot groups to spread out more than normal and at 100 feet it was basically overpowering the bbs.

KM Teflon 407mm x 6.04mm barrel test

0.20 Elite bbs: Average fps = 346.7
Chrono’ed 10 shots: 344.6, 347.2, 346.8, 347.0, 348.0, 345.1, 346.6, 346.2, 348.7, 346.3

0.25 TSD bbs: Average fps = 314.1
Chrono’ed 10 shots: 315.2, 312.4, 315.3, 315.6, 314.1, 317.2, 313.8, 312.7, 309.6, 314.6

0.28 TSD bbs: Average fps = 284.0
Chrono’ed 10 shots: 285.9, 287.3, 285.0, 283.1, 282.8, 285.0, 281.4, 282.5, 286.4, 280.1

For the sake of curiosity I retested the 407mm KM barrel to see what difference there might be when compared to the first test. Since the bb speed is 30fps less than on December 7th, the comparison could be revealing. As it turns out the accuracy is about the same. The 0.20 groups are very close to being the same, this 0.25 group is a little more spread out, and the 0.28 group here is as tight as the 0.25 group on Dec. 7th. If you factor in the wind effect there would probably be tighter groups for all three of these bbs.

Promethius 363mm x 6.03mm barrel test

0.20 Elite bbs: Average fps = 326.0
Chrono’ed 10 shots: 327.2, 325.5, 326.3, 326.2, 324.5, 327.1, 329.2, 325.0, 324.8, 323.9

0.25 TSD bbs: Average fps = 295.0
Chrono’ed 10 shots: 296.3, 294.0, 296.3, 292.5, 295.5, 295.3, 293.2, 298.8, 294.4, 293.8

0.28 TSD bbs: Average fps = 265.3
Chrono’ed 10 shots: 267.2, 264.9, 265.0, 268.4, 264.1, 268.1, 262.4, 262.3, 262.0, 268.1

This inner barrel was the one I was hoping would show much improvement in accuracy. And I was not disappointed with the results. All three 50-foot groups were by far the best of the tests especially considering the windy conditions. The one surprise was the loss of fps when using this tightbore barrel compared to the other tightbores. I suppose there is a chance I didn’t get the hop-up just right so that maybe I lost some compression.

Here is where I start throwing around some opinions and observations that is subject to interpretation and a lot of what if questions. As a result of the tests the following items became obvious to me.

1. The lack of consistency in fps from one shot to the next is the biggest enemy of accuracy in the standard AEG. When you get a 3 to 8 fps difference in a ten shot group there is no way to get the kind of groups a real marksman is used to. And when that difference is trying to reach out beyond 100 feet you basically have a slug shooting, rapid-fire shotgun.

2. I constantly worried that the hop-up was not exactly the same for each barrel. When I was pushing a new barrel into the hop-up there just seems to be too much chance that the bucking will not be in the exact same position as it was for the barrel before. The results were consistent enough to make me think this was not the problem I envisioned but I would like to think there is a better way.

3. This test was not nearly exhaustive enough to learn all there is to learn about the effectiveness of the various barrel options.

4. The variability of the weather conditions makes some of the results open to some sort of weighted comparison rather than a straight one-for-one comparison.

5. Regardless of inner barrel I was most impressed with how 0.25 and 0.28 bbs improved accuracy. And when dealing with wind and underbrush there is no substitute for a heavy bb.

6. There is an accuracy improvement over the stock barrel in the CA G36c when I use a tightbore inner barrel. And, the accuracy improvement of the 6.03mm Promethius barrel over the 6.04mm KM barrels is fairly significant in this test. Testing a 6.01mm inner barrel would possibly add interesting results regarding how a tighter bore could make a more accurate gun.

7. The difference in accuracy between the KM 407mm and KM 300mm barrels was not significant enough to be a distinct advantage one way or the other. Length of barrel did not make much difference in these tests.

In a nutshell: A tightbore inner barrel will increase accuracy over stock barrels. Heavier bbs will increase accuracy over lighter bbs. The TK Twist barrel has serious effective limits and should only be considered for low-powered (under 330 fps) AEGs. There seems to be a correlation between smaller bore diameter and increased accuracy.

In the final analysis, you will have to be the one to determine if a 10 or 25% increase in accuracy is worth the cost of a tightbore.

If I get additional barrels to test I may add to this investigation but for now, just remember, if your AEG isn’t accurate you can make up for it with strong tactics and skillful application of those tactics.